The present invention relates to a rod-shaped mesoporous powder, a humectant adsorbing powder and a cosmetic preparation using the same, and in particular, relates to an improvement of a shape of the powder, and an improvement of shelf life of the cosmetic preparation using the same.
A so-called mesoporous powder which has a mesopore of 2 to 50 nm pore size attracts attention as an adsorbent of gas or liquid, or as a carrier of a catalyst.
For example, a mesoporous powder which is disclosed in Japanese Unexamined Patent Publication No. Hei 8-67578 is composed of a three-dimensional structure which is made of a silicate and has a relatively uniform pore of 1.5-10 nm.
As for a manufacturing process of the mesoporous powder, a process for forming a three-dimensional structure by introducing a surfactant to an interlayer of a layer silicate such as kanemite and removing the surfactant with calcination or by removing a surfactant after gathering a silicate around the surfactant which was gathered in liquid with micelle state and the like are developed.
However, a particle size of the mesoporous powder is prescribed to the particle size of the layer silicate in the former process which uses the layer silicate. Also, since the mesoporous powder is laminar, it is feared that fluid resistance per pore degree is increased in the case where the mesoporous powder is used as a column packing.
On the contrary, though examples of manufactured rod-shaped porous powders which are reported (Science Vol. 273 pp. 765-767), every rod porous powder has a considerably large size. In particular, the external diameter is approximately 3 xcexcm and the pore size becomes big. This is far from mesoporous in size when the pure silicic porous powder does not contain aluminum. Therefore, a specific surface area becomes relatively small and there is a problem that the process is limited to use only for a molecular sieve. Also, a rod-shaped mesoporous powder of certain fine particle size can be manufactured in the case where aluminum is contained in the powder. However, it is feared that catalytic activity becomes high due to the presence of aluminum. This process is also unfavorable.
On the other hand, as a powder cosmetic preparation, there is a powder of a loose form such as a white powder, a baby powder, and a body powder, and solid form including an excipient for hardens.
These powder cosmetic preparations are widely used for makeup repair, and keeping the skin healthily due to the absorption of sweat and sebum by the powder.
In the prior art, the powdery cosmetic preparation included no water. Recently the importance of humectance has been recognized. As a result, it is desired to add humectant in a powdery cosmetic for good humectance.
However if a large mount of high water-absorbing material such as a humectant is compounded in a powder cosmetic preparation, the water-absorbing powder cosmetic preparation itself increases and the expansion and sweating may appear in the product.
Therefore, it was substantially impossible to blend a large amount of humectant to obtain the moisturing effect satisfactory, even if it is possible to blend small amount of humectant with a powder cosmetic preparation.
In view of the above-mentioned problems of the prior art, a first object of the present invention is to provide a rod-shaped mesoporous powder which is mainly comprised of silicon oxide and has homogenous pore.
Also, a second object of the present invention is to provide humectant adsorbed powder that can improve stabilization of a product and also has an excellent humectance, and a cosmetic preparation using the same.
As a result of diligent studies by the inventors for attaining the above-mentioned objects, it has been found that a fine diameter rod-shaped mesoporous powder can be obtained by reacting a silicate which has a specific ratio of silica/alkali metal under a specific concentration.
Namely, a rod-shaped mesoporous powder in accordance with the present invention is mainly composed of silicon oxide and has almost homogenous pore, and is obtained by a process which comprises the step of,
a dissolution step wherein a concentration of 0.3-1.2M of a silicate which is in the range of 0 less than SiO2/Y2O less than 2 (Y: alkali metal atom) is dissolved in the presence of a cationic surfactant and the pH is 11 or more,
a condensation step wherein the pH is adjusted to 10.5 or less within 30 minutes, a rod micelle is formed with said cationic surfactant and a silicate is condensed on said rod micelle, and
a removal step wherein said cationic surfactant is removed from a micelle state condensation which has an outer shell made of the silicate by said condensation.
Also, in said powder, it is preferable that whose outer diameter is 20-200 nm and a mesopore is elongated to its longer direction.
Also, in said powder, it is preferable that a primary particle is formed by aggregating two or more of rod substances in network state.
The humectant adsorbing powder in accordance with the present invention comprises the rod-shaped mesoporous powder and a humectant adsorbed in the powder.
Also, in said powder, it is preferable that the adsorption rate of said humectant is 1 to 90% by weight of the total of a humectant adsorbed powder.
When the adsorbing rate of the humectant falls below 1 wt %, the actual effect of the moisture disappears. When the adsorbing rate of the humectant exceeds 90 wt %, it exceeds the limit of the sweat and sebum absorption action of the powder.
Namely, a cosmetic preparation in accordance with the present invention comprises said humectant adsorbing powder.
Also, in said cosmetic preparation, it is preferable that the content of humectant adsorbing powder is 0.1 to 90% by weight of the total of a cosmetic preparation
When the content of humectant absorbing powder falls below 0.1 wt %, the actual effect of said humectant absorbing powder is not sufficiently obtained. When the content of humectant absorbed powder exceeds 90 wt %, the product is hardly obtained.